Atrial tachycardia occurs when the atrial rate exceeds 100 bpm and the origin of electrical activity is within the atrium but outside the sinus node. Paroxysmal atrial tachycardia (PAT), especially with second-degree AV block (PAT with block) classically is associated with digitalis toxicity.
Multifocal atrial tachycardla often is associated with chronic obstructive pulmonary disease and heart failure (HF) and may be potentiated by concomitant therapy with theophylline. Therapy is targeted at the underlying pathophysiologic process.
The ECG typically reveals an atrial rate of 100-200 bpm and may be observed to increase and decrease over time. The P waves have an abnormal configuration and axis, the PR interval depends on the atrial rate, and the QRS pattern is either normal or reflects aberrant conduction secondary to the increased rate.
PAT with block in the setting of digitalis therapy should be treated by discontinuing digitalis and maintaining normal serum potassium levels. If refractory and symptomatic, treatment with digoxin antibodies and (if necessary) with lidocaine, propranolol, or phenytoin should be considered.
In clinical situations not associated with digitalis toxicity calcium channel antagonists, beta-adrenergic antagonists, or digitalis may be used to slow the ventricular response rate.
If atrial tachycardia persists, class Ia, Ic, or III agents can be added. Unifocal or re-entrant atrial tachycardias often can be eliminated permanently with radiofrequency catheter or surgical ablation.
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